The present disclosure relates to a vehicle air conditioner including a heat pump device which performs heating and defrosting modes of operation.
A vehicle air conditioner with a heat pump device has been mounted on a car and other kinds of vehicles (see, for example, Japanese Unexamined Patent Publication No. 2010-111222). The heat pump device includes a compressor, an interior heat exchanger, an expansion valve, and an exterior heat exchanger. An interior fan to blow air toward the interior heat exchanger is provided inside the vehicle cabin, and an exterior fan to blow air toward the exterior heat exchanger is provided outside the vehicle cabin.
During heating, the interior heat exchanger functions as a radiator, and the exterior heat exchanger functions as a heat absorber. If frost is formed on the exterior heat exchanger during heating, the operation modes are switched into a defrosting operation mode to supply a high-temperature refrigerant to the exterior heat exchanger. According to Japanese Unexamined Patent Publication No. 2010-111222, the exterior fan is stopped during the defrosting mode of operation, and when the defrosting mode of operation ends, the airflow rate of the exterior fan is maximized to blow off the water deposited on the exterior heat exchanger.
In general, the exterior heat exchanger is rarely frosted uniformly, if ever, and in most cases, has a region that frosts easily during heating and a region that does not frost easily during heating. Furthermore, depending on the configuration and operating state of the heat pump device, sometimes more heat may be dissipated, and frost may be formed more easily, in a region closer to a refrigerant outlet of the exterior heat exchanger than in a region closer to a refrigerant inlet thereof.
Once the exterior heat exchanger is frosted albeit just partially, the frost tends to grow from there and eventually cover the exterior heat exchanger entirely. That is why if the formation of frost on such an easily frostable region can be delayed as much as possible, the heating performance capacity is improvable.
In view of the foregoing background, it is therefore an object of the present disclosure to improve the heating capacity, and eventually increase the occupant's comfortableness, by delaying the formation of frost on such a region closer to the refrigerant outlet of the exterior heat exchanger as much as possible if the region closer to the refrigerant outlet tends to frost more easily during heating operation than another region closer to the refrigerant inlet of the exterior heat exchanger.